The present invention relates to an apparatus and method for automatically controlling a quantity of light received in an image pickup device.
An image pickup device should provide a proper light exposure so as to obtain an image with a relatively high or excellent quality. Such image pickup device may sense a signal level of a picked-up image and automatically control an iris diaphragm of the image pickup device in accordance with the sensed signal level. However, in sensing or detecting such signal level, the image pickup device may sense the signal level of the entire or overall image which may include the background thereof. As a result, the aperture value of the color image pickup device is influenced by such sensed signal level. As such, the signal level due to the picked-up background image may obstruct or adversely affect the proper aperture value for a desired target object. In other words, the brightness of the background may hinder obtaining a proper brightness condition for the target object. For example, a target object may be made shadowed in a backlighted condition, and subject to halation in an excessively lighted condition.
Further, to provide a correct exposure, the image pickup device may perform automatic iris control which changes an interior divisional ratio of a peak value to an average luminance level of an overall screen for shifting a target value to a bright or a dark side. Such control may produce an adverse effect on the aperture value of a highly luminous portion however long the area may be. Moreover, the difference between the peak value and the average luminance level may be relatively small and may result in a disadvantageous restriction in the amount of shifting.
Furthermore, as previously described, the image pickup device may perform iris control for the overall screen. As such, the image pickup device may not provide a proper aperture value for a specific area of the screen.